The role of carbohydrate structures of human chorionic gonadotropin (hCG) in gonadotropic action and subunit association was the focus of this study. Production and purification of hCG specific antibodies were also undertaken. A. The measurement of the rate of fluorescence enhancement of 1-anilinonaphthyl-beta-sulfonate when complexed with intact or HF-deglycosylated hCG revealed that the subunits of deglycosylated hCG reassociated nearly 10-fold faster than unmodified subunits. Studies on the reassociatin rate of hybrid subunits from the intact Beta-subunit of ovine luteinizing hormone and subunits of intact an modified hCG suggest that carbohydrates moieties in the Alpha-subunit dominant the reassociation behavior. B. Antibodies raised against HF-deglycosylated hCG and a bivalent F(ab')2 fragment prepared and purified from a sequence-specific anti-carboxymethylated hCGBeta antibody were shown to enhance stimulation of cAMP and progesterone production in rat differentiated granulosa cells preincubated with the modified hCG. These findings are consistent with the notion that hormonal activation may be caused by cross-linking and/or microaggregation of the HF-hCG:receptor complex. However, antibodies which bind to an appendate of HF-hCG too flexible and distinct from the complex or which have the ability to strip off hormone from the receptor complex were ineffective in eliciting activation.